Field of the Invention
The present invention relates to polyacrylamides, and more particularly ionic polyacrylamides aided by silicon polyether copolymers for use as for example, friction or drag reducers used in water based hydraulic fracturing fluid, water purification and drilling mud additives.
Background of the Art
Polyacrylamides (PAM) are widely used as soil stabilizers, water purifier and friction reducers in agriculture, water and oil & gas industries, respectively. In the oil & gas industry, PAMs are used as additives in fracturing (fracking) and drilling applications. In fracturing, a large volume of water is injected under high pressure into the formation in order to fracture the rock formation (shale, sandstone, limestone, etc.) and this way deliberating crude oil and/or natural gas from the pores. In hydraulic fracturing applications, high molecular weight anionic and cationic polyacrylamides are used as friction reducers where the hydrated polymer suppresses the turbulence present in high velocity gradient water. Since hydraulic fracturing is performed at very high injection rate, reduction of pumping pressure as a results of friction reduction will result in less power consumption by the pumps and thus the use of effective friction reducers in the fracturing fluid can decrease the cost of the operation by a large margin.
The polyacrylamide molecules are sensitive to high shear, temperature and the ionic strength of the water used to solubilize them. At very high shear rate high molecular weight polyacrylamides are susceptible to breakdown into smaller chains. At high temperature and in alkaline conditions polyacrylamides hydrolyze to form acrylate fractions in the polymer chains, which produce negative charges on the polymer chains. The degree of hydrolysis increases with the temperature. Hydrolyzed polyacrylamides can remain stable in aqueous solutions in the absence of multivalent cations, such as Ca2+, Mg2+, Fe3+, etc. However, as the concentration of these ions increases in water, the hydrolyzed polymers become more susceptible to form a complex with these ions and precipitate out from the water solution. The precipitated polyacrylamides do not hydrate effectively and the friction reduction diminishes. The, precipitated polyacrylamide clusters or particles can also damage the rock formations leading to reduced production of crude oil and/or natural gas.
In many of the fracturing jobs where fresh water is not accessible, formation water, frac fluid flow back water or recycled frac flow back water is frequently used. This water contains high concentration of monovalent and multivalent cations and anions. Therefore, a higher amount of friction reducer is needed to achieve the desired hydration of the polymer and friction reduction in such water. Increasing demand for fracturing water leads to consumption of more fresh water resources. Therefore, friction reducers, which can perform in all kinds of water, are desired.
The present invention discloses new friction reducer compositions for water based liquids comprising an ionic polyacrylamide and a silicon polyether, which are capable of delivering faster inversion of polyacrylamide emulsion and better hydration of the polymer chains needed to achieve maximum friction reduction in the brines consisting of high amount of monovalent cations, monovalent anions and multivalent cations. The silicon polyether copolymers disclosed in this invention are designed to be compatible with polyacrylamide emulsions.